Periodic cleaning and sanitizing in pharmaceutical, dairy, food and beverage industries, in food preparation and service businesses are a necessary practice for maintaining product quality and public health. Residuals left on equipment surfaces or contaminants found in the process or service environment are undesired since there is a risk that they promote growth of microorganisms. For protecting the consumer against potential health hazards associated with pathogens or toxins and maintaining the quality of the product or service in food and pharmaceutical industries it is necessary to routinely remove residuals and contaminants from surfaces of the equipment used in the pharmaceutical and food industries which usually is made of aluminum or colored metals like zinc, cadmium, copper, cobalt, nickel, bismuth, tin and lead or alloys thereof, in particular brass and bronze.
An efficient and economical way to remove undesired residuals and contaminants from hard surfaces of such metals and alloys thereof is the use of cleaner compositions which contain alkaline components besides wetting detergents. However, under alkaline conditions the protective oxide layer normally present on surfaces of aluminum and colored metals is removed and as a result thereof the bare metal surface will be heavily corroded. In many applications use of the most corrosion-resistent materials may be not economical or use of a material having a satisfactory corrosion resistance may not be known. Other methods of avoiding corrosion, such as by using glass, ceramic and inorganic coatings may be prohibitively expensive or incompatible with other process conditions. In all these cases an alternative approach is to minimize the corrosion by adding corrosion inhibitors to corrosive cleaning compositions. A further common way for preventing corrosion of colored metals in the pharmaceutical, food and beverage industries is the use of silicates having the disadvantage that unremovable residues may remain on the cleaned surfaces.
From U.S. Pat. No. 5,723,418 it is known to use lubricant compositions for conveyor systems which may transport food substances. The lubricant compositions disclosed therein may contain polycarboxylic acids such as carboxylic diacids, triacids or phosphate esters like alkyl or alkylaryl phosphate mono esters as corrosion inhibitors. According to U.S. Pat. No. 5,925,601 lubricants for conveyors moving glass, metal or plastic containers for the beverage market may contain phosphate esters like alkyl or alkylaryl phosphate mono esters or triazoles such as benzotriazole, tolyltriazole, and mercaptobenzothiazole as corrosion inhibitors. From U.S. Pat. No. 5,393,464 corrosion inhibitors in aqueous media are known which comprise N-ethoxy-2-substituted imidazoline, the N-ethoxy substituent having from 1 to 30 ethoxy units and the 2-substituent being an unsaturated fatty chain having from 6 to 30 carbon atoms.